/*
 * Created on Oct 08, 2004
 * Created by Alon Rohter
 * Copyright (C) Azureus Software, Inc, All Rights Reserved.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version 2
 * of the License, or (at your option) any later version.
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
 *
 */
package com.aelitis.azureus.core.util.average;

/**
 * Implements an exponential moving average.
 */
public class ExponentialMovingAverage implements Average {

    private final float weight;
    private double prevEMA;

    /**
     * Create a new exponential moving average which smooths over the given number of periods.
     */
    public ExponentialMovingAverage(final int periods) {
        if (periods < 1) {
            System.out.println("ExponentialMovingAverage:: ERROR: bad periods: " + periods);
        }
        this.weight = 2 / (float) (1 + periods);
        this.prevEMA = 0;
    }

    /**
     * Create a new exponential moving average, using the given smoothing rate weight.
     */
    public ExponentialMovingAverage(final float weight) {
        if ((weight < 0.0) || (weight > 1.0)) {
            System.out.println("ExponentialMovingAverage:: ERROR: bad weight: " + weight);
        }
        this.weight = weight;
        this.prevEMA = 0;
    }

    public void reset() {

        this.prevEMA = 0;
    }

    /**
     * Update average and return average-so-far.
     */
    public double update(final double newValue) {
        prevEMA = (weight * (newValue - prevEMA)) + prevEMA;
        return prevEMA;
    }

    /**
     * Return average-so-far.
     */
    public double getAverage() {
        return prevEMA;
    }

}